Welcome to the forums. You mentioned sprites. Here’s high-resolution Wolfenstein 3D and WolfenDoom textures: http://www-personal.umich.edu/~jimw/ClassicFPS/ . Jim W isn’t making high resolution textures anymore. I suppose that if you’re really ambitious, then you could work on high-resolution Spear of Destiny textures.

An acquaintance and I were working on a project that's been put on hold. We wanted to make Greek Mythology sprites for Wolfenstein 3D.